Anatomy & Physiology Exam 3 (Ch. 8-10)

Vestibular System

•Ampulla is the expanded region of the semicircular canals •Each ampulla houses a crista ampularis: receptor organ for movement -Made up of ciliated receptor cells and a supporting membrane •The crista is the receptor organ for movement; made up of ciliated receptor cells and a supporting membrane •From each of the 6000 receptor cells protrude almost 50 stereocilia (minute hairs that sense movement in fluid)

Outer Ear: Tympanic Membrane (cont'd)

•Anterior & Posterior Malleolar Folds: recess on either side of pars flaccia; result of malleus pushing distally on the membrane to transmit acoustic energy from tympanic membrane to ossicular chain

Middle Ear: Anterior Wall (removed)

•Entrance to the Eustachian tube (auditory tube) •Responsible for aeration of middle ear •Connects middle ear and nasopharynx •Maintains equilibrium between pressure in middle ear and atmospheric pressure •36mm long (12mm of bone terminates at the juncture of squamous and petrous parts of temporal bone; rest is cartilaginous) •Cartilaginous auditory tube is twice as long as the bony tube

Outer Ear: Tympanic Membrane (cont'd)

•Fibrous intermediate layer -Consists of two layers of fibers: •radial & circular fibroelastic tissues •provide optimal strength and tension

Horizontal Vertical Canal

•Horizonal vertical canal senses movement roughly in the transverse plane of the body •It's ampulated end enters the vestibule near that of the anterior semicircular canal, above the level of the oval window

Middle Ear

•Houses three articulated bones that provide the means for transmission of acoustic energy through the tympanic membrane to the inner ear •By birth, the middle ear is adult size and the ossicles are almost as large as they will ever b

Pharyngeal Stage (cont'd)

•Hyolaryngeal Elevation: movement of the hyolaryngeal complex (hyoid + larynx) begins with anterior movement of the tongue base and tongue tip at the initiation of the swallow; simultaneously the hyoid and larynx elevate •Pressurization of the Pharynx: driving force behind bolus propulsion into the esophagus •Airway Protection: vocal folds tightly adduct at the initial stage of the swallow; false folds close and epiglottis inverts to cover laryngeal inlet/aditus •Pharyngeal Timing: product of a central pattern within the brain stem that orchestrates the series of movements; once initiated, the pattered activity will continue to it's conclusion

Inner Hair Cells

•IHC are not embedded within tectorial membrane •Results from fluid flow and endolymph turbulence •At the point of maximum excursion, basilar membrane is humped up, protruding into the fluid stream; At this constriction, velocity of the fluid flow increases (Bernoulli effect) •This disturbance at the point of maximum excitation causes a turbulence producing swirls of fluid molecules causing hair cells to become excited

Tympanic Muscles: Stapedius

•Imbedded in posterior wall of middle ear •Inserts into posterior neck of stapes •Rotates footplate of stapes posteriorly; stiffening ossicular chain •About 6mm long; 5mm2 in area •Only tendon emerges from the pyramidal eminence in the middle ear space •Innervated by Stapedial Branch of VII: Facial Nerve

Rooting & Sucking Reflexes

•Important for neonates and infants •Rooting Reflex: tactile stimulation of cheek (perioral region) causes infant's head to rotate toward the stimulus and mouth to open •Sucking Reflex: created by soft contact with inner margin of lips •Causes a sucking response involving generating a labial seal (contraction of the upper and lower orbicularis oris) and protruding and retraction of tongue

Overactive Cerumen

•Individuals that have overly active ceruminous glands may find that the EAM becomes occluded •Removal of the cerumen may be required •Attempts to remove cerumen with a cottons swab may result in cerumen and dirt begin packed against the inferior boundary of the TM

Vestibular Mechanism (cont'd)

•Information is integrated with the following to form the perception of body position: -Joint sense -Muscle spindle afferents -Visual input

Cochlear Duct

•Membranous labyrinth of cochlea •Fluid inside cochlear duct is known as endolymph •Resides between scala vestibuli and scala tympani making up scalamedia which houses sensory apparatus of hearing •Ressiner's Membrane: extremely thin separation between perilymph of scala vestibuli and endolymph of scala media •Basilar Membrane: forms floor of scala media, separating scala media and scala tympani, housing organ of hearing

The Middle Ear

•Middle ear is related to the following structures: -Tympanic Membrane -Ossicles -Entry to the Cochlea -Oval Window •Responsible for increasing the pressures arriving at the cochlea -Cochlea is a fluid-filled cavity -- without pressures of the middle ear, talking to someone would be like talking to someone under water •When the pressure increases, there is a resistance to flow of energy (impedance)

MBSImP

•Modified Barium Swallow Impairment Profile •A 17-item scale to rate swallows done during a videofluoroscopic evaluation. •Components of Oral Phase: 1. Lip Closure 2. Tongue Control/Bolus Hold 3. Bolus Preparation/Mastication 4. Bolus Transport/Lingual Motion 5. Oral Residue 6. Initiation of Pharyngeal Swallow

Salivation

•Motor response •Result of production and release of salvia into the oral cavity •Component of taste, mastication, and deglutition •Stimulated behaviorally by the sight, smell, and taste of food •Salivary glands produce 1.2 liters of saliva per day (production is reduced during sleep) •Xerostomia: reduced salivary output caused by some medications and diseases (dry mouth)

Tympanic Muscles

•Muscles of middle ear attached to ossicles •Smallest muscles of the human body -Stapedius -Tensor Tympani

Ossicles: Stapes (cont'd)

•Neck of stapes bifurcates to become the crura •Arch formed by the anterior and posterior crura converges on the footplate or base of the stapes •Annular Ligament: holds in place the footplate of the stapes when resting in the oval window of the temporal bone

Olfaction (cont'd)

•Olfactory sensors have a short life (60 days); continually replaced •Sensors arise from olfactory bulb and are found within the epithelial lining of the upper posterior nasal cavity •Small cilia protrude from the olfactory sensor; very specialized, transduce molecular stimulant into perception of smell that is transmitted to the olfactory bulb •More than 1000 different odors are decoded by olfactory system

Facial Muscles

•Orbicularis Oris: maintains oral seal •Mentalis: elevates lower lip •Buccinator: flattens cheeks Risorius: flattens cheeks

Retch & Vomit Reflex

•Retch: involuntary attempt at vomiting; caused by noxious smells, tastes, gastrointestinal distress, vestibular dysfunction, upsetting visual/mental stimulation •Vomiting: oral expulsion of gastrointestinal contents •Vomit Response: multiple simultaneous or synchronous reflexes including: •Occlusion of the airway by vocal fold adduction, extreme contraction of abdominal muscles, relaxation of upper and lower esophageal sphincters, elevation of larynx, and velum, depression of epiglottis, elevation of pharynx, and tongue protrusion

Organ of Corti

•Similar in design to the vestibular organs •Sensory organ of hearing within the inner ear •Has four rows of hair cells •Supported by a bed of Deiters' cells (supporting cells) -Three rows of outer cells (~12,000 cells) -Single row of inner hair cells (~3,500 cells) stretching from the base of cochlea to apex

Fibroendoscopic Evaluation of Swallow (FEES)

•Superior inspection of structures via direct visualization

MBSImP (cont'd)

Components of Pharyngeal Phase: 7. Soft Palate Elevation 8. Laryngeal Elevation 9. Anterior Hyoid Excursion 10. Epiglottic Movement 11. Laryngeal Vestibular Closure 12. Pharyngeal Stripping Wave 13. Pharyngeal Contraction 14. PES Opening 15. Tongue Base Retraction 16. Pharyngeal Residue Components of Esophageal Phase: 17. Esophageal Clearance

Feeding & Speech

Feeding skills are preparatory and supportive for speech. Infant movements are gross and reflexive. •Gross movements of mandible during sucking ends up to refined movement of mandible during speech. •Tongue protrusion during sucking evolves into a sucking gesture that does not require tongue protrusion. •Gross piston-like swallow of an infant evolves into an orchestrated mature swallow.

Muscles of Esophageal Stage

Lower Esophageal Sphincter (LES): musculature at the end of the esophagus that is tonically contracted at rest to prevent material from refluxing from the stomach; relaxes during swallowing to allow fluid/food to pass into the stomach Upper Esophageal Sphincter (UES): inferior pharyngeal constrictor + upper esophageal muscles + cricopharyngeus •Separates the pharynx from the esophagus •Also known as Pharyngeal Esophageal Sphincter (PES) •Allows bolus to enter esophagus, but closes between swallows and prevents air from filling the esophagus at rest

Main Structures of the Outer Ear

Pinna (Auricle) •External Auditory Meatus (EAM) -Tympanic Membrane •See Table 9-1: Landmarks of the Outer Ear

Solid Diets

Regular Diet: •No restrictions Dysphagia III Diet: •Consists of foods that are soft and easy to chew and swallow •Nearly regular texture but excludes very hard, sticky, or crunchy foods Dysphagia II Diet: •Consists of foods that are mechanically altered by blending, chopping, grinding, or mashing so that they are easy to chew and swallow Dysphagia I Diet: •All Pureed

Liquid Diets

Thin Liquids: •No restriction/thickener Nectar Thickened Liquids: •Tomato juice consistency Honey Thickened Liquids: •Honey consistency Pudding Thick Liquids: •Pudding consistency •Less commonly used

Ossicles: Malleus

•"Like a hammer" •Largest of the ossicles •9mm long •Weighs only 25mg •Provides point of attachment with tympanic membrane (manubrium) •Contains handle and head: -Bulk of bone is the head (caput): point of articulation with incus

Otitis Externa

•"Swimmer's Ear" •Otitis Externa: inflammation of the skin of the external ear •Responds with edema (swelling) •May be quite painful if the epithelium is tightly bound to it's underlying structure (as it is in the EAM and pinna) •May result from bacterial infection following trauma, or abrasion -Can spread between clients if probe tips and specula are not cleaned •Also may result from viral infection

Electrical Events (cont'd)

•15% of ion channels are open at any time •When the cilia are pivoted toward the tallest stereocilia (kinoclium), the hair cell depolarizes •When it is tilted away from the kinoclium, the hair cell is hyperpolarized (cannot fire) •This depolarization produces a graded receptor potential that increases as the amplitude of the stimulus increases •Glutamate is released as a results of depolarization of the hair cell and used a signal to the VIII nerve fiber

Outer Hair Cell

•3 rows broadening to four rows at apex •12,000 •Approx 150 stereocilia protrude from the surface in a "W" or "V" pattern •Test tube shape •Each OHC shares innervation with 10 other OHC being innervated by the same VIII nerve fiber •Phalangeal processes replace hair cells lost through acoustic trauma, thereby maintaining the delicate cuticular plate

Innervation of Organ of Corti

•Afferent Innervation -Type I large myelinated fibers make up 95% of VIII nerve and innervate inner hair cells -Type II small myelinated and unmyelinated innervate outer hair cells •Efferent Innervation -Inhibitory, reducing output by hair cell stimulation -Helps detect signals in background noise

Tastes

•All tastes can be sensed all over the tongue (previously we thought taste receptors were restricted to zones of tongue) •Types: salty, sweet, sour, bitter, and umami •Taste sense determines whether a bolus is ingested or ejected from the mouth

Videofloroscopy

•Also known as MBSS or MBS (Modified Barium Swallow Study) •Roles - determine safety of PO intake, etiology of findings, diet recommendations •Defines anatomy and physiology of patient's oropharyngeal swallow while also measuring: •Speed of swallow (oral/pharyngeal transit time) •Efficiency of swallow •Movement patterns of structures •Penetration and Aspiration •Definitive test of oropharyngeal dysphagia

Ossicles: Malleus (cont'd)

•Anterior and lateral processes provide points of attachment for ligaments •Manubrium attaches to tympanic membrane along its length; terminating with the lateral process •Attachment of the lateral process with TM forms anterior and posterior malleolar folds and pars flaccida

Anterior Vertical Canal

•Anterior vertical canal is oriented so that it sense movement in a plane roughly perpendicular to the long axis of the temporal bone •Anterior end of the canal houses the ampulla •Other end combines with non-ampulated end of the posterior vertical canal at the crus commune

Otitis Media

•Any condition in which fluid accumulates in the middle ear cavity •Sequence: -Auditory tube stops functioning properly -Middle ear space to become anaerobic -Poorly functioning auditory tube may not allow equalization of pressure between the middle ear space and the environment •Negative pressure may build up in the middle ear space pulling fluid from the blood into the middle ear tissues (transudation) •Negative air pressure may also stimulate secretion of mucus from the middle ear tissue •Middle Ear Effusion: creates a barrier to sound transmission as movement of tympanic membrane is greatly inhibited

Tympanic Muscles: Tensor Tympani

•Arising from anterior wall of middle ear space (superior to orifice of Eustachian tube) -Muscle originates from te cartilaginous portionof the eustachian tube •Inserts into upper neck of malleus •Pulls malleus anteromedially -reducing the range of movement of TM by placing indirect tension on it; stiffens ossicular chain •Contraction of stapedius and tensor tympani reduces the strength of the signal reaching the cochlea - potential protection •Approximately 25mm in length and nearly 6mm2 in cross-sectional area •Innervated by the V: Trigeminal Nerve

Swallow Pattern of Neonate (cont'd)

•Around 6 months, teeth erupt and first solid food is introduced. •Teeth block anterior protrusion of tongue and support retraction of tongue during swallowing. •Teeth support chewing and grinding à strengthen muscles of mastication •Mature swallow of adults requires contraction of masseter, temporalis & medial pterygoid muscles to put force of tongue upon the roof of mouth as bolus is propelled backward. •This force is important in development of dental arches and hard palate.

Mastication & Deglutition (cont'd)

•As food is received, all muscles inserting into the orbicularis oris contract, resulting in opening, closing, pursing, and retracting the lips. •All intrinsic and extrinsic muscles of the tongue contract to move the food into the position for chewing and preparation of the bolus for swallowing. •Velar elevators seal off the nasal cavity to prevent regurgitation. •Pharyngeal constrictors contract to move the bolus down the pharynx and into the esophagus. At the same time, the larynx elevates. •More the 55 pairs of muscles are coordinated for the process.

Aspiration vs. Penetration

•Aspiration: passage of bolus into larynx and through the vocal folds •Penetration: passage of the bolus into the larynx

Functions & Structures of Hearing

•Auditory system is the only communication system that has no other function besides communication. •The ear is an energy transducer converting acoustic energy into electrochemical energy. •Audition: the process associated with hearing; vital part of verbal communication •Main structures of the ear: -Outer -Middle -Inner -Auditory Pathways

Outer Ear: Pinna

•Auricle •Prominence referred to as "the ear" •Structure provided by a cartilaginous framework •Collector of sound that is processed in the middle ear and cochlea •Function: aiding localization of sounds in space; capturing sound energy

Malformations of Pinna & EAM

•Auricular Malformations: arises from issues in embryological development •Auricular Deformations: arises from effects of physical forces on prenatal structures •Auricle develops between 5th and 9th prenatal week - malformations can raise from effects of multiple genes as well as introduction of teratogens

Outer Ear: Pinna (cont'd)

•Auricular cartilage is a unitary structure covered with a layer of epithelium invested with fine hairs that are useful for keeping insects and dirt out of the ear canal

Osseous Semicircular Canals (cont'd)

•Binaural orientation of the two semicircular canals is such that the anterior semicircular canal of one ear is parallel to the posterior canal of the other •Horizontal planes lie in the same plane but the ampullae are in mirror-image locations •The brain can differentiate rotary movements toward the left vs. right •Utricle and saccule are responsible for mediating the sense of acceleration of your head ins pace such as in sudden movement of falling

Ossicles: Incus (cont'd)

•Body of incus articulates with the head of malleus •Short process projects posteriorly while end of the long process bends medially; forming lenticular process with which the stapes will articulate

Middle Ear Function

•Buckling of Tympanic Membrane -TM buckles/moves in response to sound such that arm of malleus moves a shorter distance that the surface of tympanic membrane resulting in reduction in velocity of displacement of the malleus, increasing force -Provides 4 - 6 dB increase •Combined, the area, level and buckling effects result in a single gain of 31 dB, from tympanic membrane to cochlea -If middle ear was removed, a signal entering EAM would have to be 31 dB more intense to be heard. -A serious impact in audition in cases of otitis media, otosclerosis, or glomus tumors can have a serious impact on the conduction of sound to the inner ear.

Oral Stage

•Can be voluntary or involuntary - you can willingly move bolus into oropharynx or it may arise as part of the involuntary, automatic sequence that leads to the pharyngeal/esophageal stages. •Tippers vs. Dippers •Front to back "squeezing" motion •Variability in tongue movement; either elevation of the tip or depression of the tip during swallow

Osseous or Bony Labyrinth

•Cavities (tunnels) within which the membranous labyrinth are housed •Embedded in the petrous portion of temporal bone (densest bone in the body) •Epithelial lining secretes perilymph -Fluid found within the superficial cavities of the labyrinth

Basilar Membrane (cont'd)

•Characteristics (cont.) -Mass increases à frequency decreases -Basilar membrane becomes increasingly massive from base to apex -Basilar membrane becomes progressively wider from base to apex -Graded stiffness, graded mass, and graded width combine to make basilar membrane an excellent frequency analyzer -Traveling wave always travels from base to apex due to impedance gradient of basilar membrane

Outer Hair Cells

•Cilia of OHC are embedded within tectorial membrane •Hair cells displaced as traveling wave moves along basilar membrane •This produces shearing action which is greatest at the point of maximum perturbation of basilar membrane •Excitation of outer hair cells result of shearing effect on cilia

Electrical Events

•Cochlea: spectrum analyzer + transducer •Mechanical properties of Organ of Corti provides spectral analysis •Stimulation of hair cells permit mechanical energy arriving at the cochlea in the form of movement of footplate of stapes to be converted into electrochemical energy •Initiation of electro events in cochlea depends on stereocilia -Minute cilia protruding from surface of hair cells •When basilar membrane is displaced toward scala vestbuli; hair cells are activated and electrical potentials are initiated •When basilar membrane is displaced toward scala tympani; electrical activity of hair cells is inhibited

Outer Ear: Pinna (cont'd)

•Concha (Concha Auricle): entrance to ear canal/EAM -Cymba Conchae: anterior extension of helix marking the anterior entrance to the concha -Cavum Conchae: deep portion of concha •Tragus: flap of epithelium-covered cartilage •Antitragus: posterior and inferior to the tragus

Osseous Semicircular Canals

•Contain sense organs for movement of the body in space •Responsible for sensation of movement of the head in space •Picture three rings attached to a ball (the vestibule); each ring in a plane at a right angle to the other rings •Interaction of the 3 permits the brain to code three-dimensional space

Pharyngeal Stage

•Contains a series of reflexively controlled events •Begins when bolus reaches faucial pillars (or posterior base of the tongue) •Beings with elevation of velum separating nasopharynx from oropharynx •Respiration stops reflexively at this point •Velum elevated, tongue retracted, lips sealed, oral and nasal cavities closed •Air cannot escape or enter for respiration When food is entering the pharynx, the airway must be protected

Bony Vestibule (cont'd)

•Contains three major recesses: -Spherical: minute perforations, passages through which portions of vestibular nerve pass to the saccule of membranous labyrinth -Cochlear: provides a similar communication between vestibule and basal end of cochlear duct -Elliptical: provides communication between the utricle it houses and the ampullae of the superior and lateral semicircular canals

Osseous Vestibule

•Contains: -Utricle (membranous) -Saccule -(membranous) -Both Utricle and Saccule contain maculae •Anterior-posterior dimension of vestibule is 5mm; width is 3mm •Filled with perilymph •Oval window is within lateral wall of vestibule

Oral Preparatory Stage (Mastication)

•Coordination is key! •Bite a cracker; count the number of times you chew (~ about 15-30 times before you swallow) •Person-to-person consistency of bolus varies: We do not have to worry about how we create the bolus (e.g. how many times we chew) but we are aware of the outcome. •When we create the "ideal" bolus; the swallow is initiated

Innervation of Taste

•Cranial Nerve VII: Facial Nerve - mediates sense of taste from anterior 2/3 of tongue (specifically sweet, salty, sour); taste sensors in palate •Cranial Nerve IX: Glossopharyngeal Nerve - transmits information from the posterior 1/3 of tongue •Cranial Nerve V: Trigeminal - mediates chemesthetic sense •Non-taste sensors (thermal and pain receptors) •Cranial Nerve X: Vagus- taste receptors of epiglottis and esophagus

Basilar Membrane

•Determination of ability to analyze frequency -Graded thickness, stiffness, and width -Traveling wave can be stimulated in the absence of middle ear mechanism (bone-conduction testing) •Characteristics -Thinner, stiffer, and narrower at base than at apex -Stiffness increases, frequency increases -Stiffness decreases in a graded fashion from base to apex -Cochlear duct is flaccid at apex where it is not connected to bony labyrinth to form helicotrema

Electromyography (EMG)

•Discussed in Chapter 7 •Measures muscle function during swallowing •Electrodes placed on a surface which allows motor potentials to be read as muscle movements

Osseous Cochlear Labyrinth (cont'd)

•Divided by the osseous spinal lamina into incomplete chambers: -Scala vestibuli -Scala tympani •Vital structure attaches to scala media (houses sensory organ for hearing) •Osseus spiral lamina becomes smaller approaching the apex •At apex, two chambers form the helicotrema (region through which the scala tympani and scala vestibuli can communicate

Outer Ear: EAM (cont'd)

•EAM is "s" shaped -You need a speculum to look at the ear canal and eardrum •Two constrictions: 1. End of cartilaginous portion and beginning of osseous 2. Isthmus; 0.5cm from the ear drum/tympanic membrane

Outer Ear: EAM (cont'd)

•EAM is approximately 7mm in diameter and 2.5cm long when measure from the depth of the concha; add 1.5cm to its length when you measure from the tragus •EAM & concha are resonating cavities; both contributing to hearing •Determination of resonant frequency depends on the length of the cavity

Electrical Events (cont'd)

•Each hair cell has about 100 channels for ion transduction (1 per cilia) •When cilia are mechanically deflected toward the highest stereocilia, the channels are drawn open •Depolarizing the inner hair cells causes excitation of the VIII nerve as a result of glutamate release •Depolarizing the outer hair cells causes a "motor" response that actually moves the basilar membrane

Outer Ear: Tympanic Membrane

•Eardrum •Separates middle ear from outer ear •Thin trilaminar sheet of tissue (3 layers) •Sits at an oblique angle in the EAM •Epithelial lining of EAM continues serves as outer layer of TM; lining of middle ear provides inner layer; Fibrous intermediate layer that provides structure

Experience of Eating

•Eating involves the following criteria: •Important for eating to be pleasant (hunger will drive people to acquire nutrition) •Food should be palatable to be eaten in sufficient amounts for good nutrition •Stages of swallowing must be supported by an adequate neuroanatomical substrate

Oral Stage

•Elevated tongue during mastication drops now and pulls posteriorly •Mastication stops; anterior tongue elevates to hard palate to squeeze bolus back toward faucial pillars •Contact with faucial pillars, velum, and posterior tongue base triggers pharyngeal reflexes •Trigger point changes over time •Geriatric swallow is triggered at a more posterior location

Multislice Computed Tomography

•Examines the kinematics of oral and pharyngeal structures •Three-dimensional representations

Outer Ear: EAM

•External Ear Canal •Terminates at the tympanic membrane •Medial 2/3 of the ear canal is housed in bony meatus of temporal bone •Lateral 1/3 of ear canal composed of cartilaginous parts, about 8mm long

Neural Responses (cont'd)

•Fiber was most sensitive to 10,000 Hz signal. As the signal frequency decreased, signal had to be of greater intensity to cause neuron to fire.

Papillae

•Fillform Papillae: dominant type; may be pink or gray, small threads on the surface of the tongue; make dorsum of tongue look rough; includes taste sensors and mechanoreceptors permitting fine discrimination of bolus characteristics •Fungiform Papillae: bright red; found interspersed with filiform papillae on tip and sides of tongue •Vallate Papillae: large, v-shaped formations of circles in posterior dorsum; each has a "moat" surrounding it •Foliate Papillae: sparsely present on the lateral margin of tongue

Esophageal Stage

•Final stage; purely reflexive - not within voluntary control •Begins when bolus reaches the entrance of esophagus •Bolus is transported through the esophagus to the lower esophageal (LES) by peristaltic contractions and gravity •Peristalsis: wave like contractions •Bolus of food enters stomach for digestion after 10-20 seconds of transit time

Neural Responses (cont'd)

•Firing rate of neurons encodes intensity of the stimulation: -As intensity increases, firing rate increases -Intensity is coded by both types of neurons: •Low-threshold neurons process low intensity signals •High-threshold neurons process high intensity signals

Outer Ear: Tympanic Membrane (cont'd)

•First Layer: Outer (cuticular) layer -Continuation of the epithelial lining of EAM •Second Layer: intermediate (fibrous) layer -Superficial layer: (radial)fibers radiate out from handle of malleus -Deep Layer: circular fibers •Third Layer: Inner (mucous) layer -Continuous with the mucosa of the middle ear •Approximately 55mm2 •Slightly concave when viewed from EAM

Reflexes in Mastication & Deglutition

•Food is moved from the tongue to the molars for chewing and is mixed with saliva, production of which is triggered by taste; primarily on the anterior 2/3 of tongue •Tactile sensation with the oral cavity provides feedback concerning consistency, size, shape of bolus •Bolus is retained within the oral cavity with the help of buccal muscles and orbicularis oris •When food consistency is adequate, the mature swallow is initiated beginning with retraction of the tongue base to cause bolus to contact with soft palate/fauces •Palatal reflex is stimulated by the contact of foreign objects with fauces or pharynx causes velum to elevate

Oral Preparatory Stage (Mastication)

•Food prepared for swallowing •Tongue cups in preparation for input food •Food kept in mouth by sealing of lips; lip seal demands breathing through nose à tongue bunches up in the back and velum is pulled down to keep food into oral cavity •Tongue compresses food against hard palate; partially crushing it in preparation for teeth

Excitation of Hair Cells

•For intensities less than 40dB, OHC are important mechanisms to code intensity •IHC are essential for frequency coding •Loss of OHC do not results in complete loss of hearing, but rather elevation of the threshold of audition.

Membranous Labyrinth

•Found within the cavity of osseous labyrinth •Structure parallels that of bony labyrinth; fluid-filled sac rests within osseous labyrinth •Filled with endolymph •Houses vestibular organ and sensory apparatus for hearing •The same fluid flows through all of the membranous labyrinth making balance and hearing intimately related

Thermal Receptors & Pain Sensors

•Four classes of thermal receptors •Warm •Hot •Cool •Cold •Differ from mechanoreceptors as thermal receptors have a tonic, ongoing response; mechanoreceptors respond only when stimulated •Slow increase/decrease in temperature is more difficult to detect than a rapid change •At high temperatures, pain sensors fire instead of thermal ones •Thermal sense needs longer duration of stimulation for perception, but sensations last longer

Stages (cont'd)

•Four extremely-well orchestrated stages •1. Oral Preparatory Stage (mastication): food is prepared for swallow •2. Oral Stage (Oral Transit) (propulsion of bolus): bolus transmitted to the pharynx •3. Pharyngeal Stage (pharyngeal swallow): bolus transmitted to the esophagus involving numerous physiological protective responses •4. Esophageal Stage (esophageal transit): food is transported from the upper esophageal region to the stomach

Neural Responses (cont'd)

•Frequency Specificity: ability of cochlea to differentiate different spectral components of a signal •Characteristic Frequency (CF) of a neuron: The frequency to which a neuron responds best (CF = 3000 Hz); humans can discriminate change in frequency of signals of about 1% (we can hear the difference between 100 Hz and 102 Hz)

The Traveling Wave

•Frequency: number of vibrations per second -The number of oscillations of the TM-ossicle-footplate combination •If number of vibration of tympanic membrane-ossicle-footplate combination is 100Hz; footplate moving inward and outward 100 times per second •This periodic vibration is translated to the basilar membrane where it initiates a wave known as the traveling wave •The traveling wave separates out the frequency components of complex sounds -High-frequency sounds impinge on the inner ear and cause vibration of the basilar membrane closer to the vestibule -Low-frequency sounds result in a long traveling wave that reaches toward the apex -When a sound has both high-and low-frequency components, those components are separated out and processed at their respective portions of the basilar membrane

Inner Hair Cell

•Hair cells on the modiolar side of the tunnel of Corti •Teardrop shape (gourd shaped) with broad base and narrow neck •3,500 cells form a single row stretching from base to apex •Upper surface of each cell is graced with a series of 50 stereocilia in a "U" pattern •Each IHC connected with VIII nerve fibers

Outer Ear: Pinna (cont'd)

•Helix: forms curled margin of pinna, making its most distal borders •Auricular Tubercle (Darwin's Tubercle): superior-posterior bulge on helix •Antihelix: immediately anterior to the helix; similar fold of tissue marking entrance to conch

Neural Responses (cont'd)

•Histogram (bar graph) -Display of data arrayed with reference to its frequency of occurrence -Helpful method of examining data over time -Data recorded on a bar graph •Post-Stimulus Time (PST) Histogram -Plots of neural responses relative to the onset of the stimulus -Verifies concept of frequency specificity •Ability of cochlea to differentiate spectral components of a signal •Auditory Physiologists: -Record bursts of electrical activity of a single neuron and plot their responses

Mastoiditis

•Inflammation of the mastoid bone •Serious condition that can result in unilateral deafness and even infection of the brain (death) •Bacteria enters the auditory tube, migrates to middle ear, and subsequently the air cells of the mastoid •Infection can then spread to the dura mater lining of the brain within the middle cranial fossa causing bacterial meningitis •Typically related to chronic otitis media •Can cause infection of the cochlea and vestibular mechanisms and may result from permanent sensorineural hearing loss, vestibular dysfunction, and tinnitus

Cough Reflex

•Initiated by noxious stimuli of the pharynx, larynx, or bronchial passageway •Involves laryngeal adduction and abdominal contraction •Increases subglottal pressure •Produces forceful exhalation

Neural Responses (cont'd)

•Interspike Interval (ISI) •Record interval between successive firings of a neuron •Provide details of the temporal structure of the VIII nerve response •Neurons need 1ms to recover from depolarization -Reveal phase-locking of neurons to stimulus period (phase-locking refers to quality of neuron wherein it responds to period of stimulation) •VIII nerve fibers responds to phase of signal, but not necessarily to every cycle of vibration

Electrical Potentials (cont'd)

•Intracellular Resting Potential -Found within the hair cells -Reveals a potential difference between endolymph and hair cells of -70 mV, giving a 150 mV difference between hair cells and surrounding fluid

Instrumentation in Swallowing

•Iowa Oral Pressure Instrument (IOPI) •Electromyography (EMG) •Pharyngeal Manometry •Multislice Computed Tomography •Modfied Barium Swallow Study or Videofluoroscopy •Fiberendoscopic Evaluation of Swallowing (FEES) or Nasoendoscopy •Ultrasound

Laryngeal Muscles

•Lateral Cricoarytenoid: adducts vocal folds •Transverse Arytenoid: adducts vocal folds •Oblique Arytenoid: adducts vocal folds •Aryepiglotticus: retracts epiglottis; constricts aditus •Thyroepiglotticus: dilates airway following swallow

Soft Palate Muscles

•Levator Veli Palatini: elevates soft palate •Tensor Veli Palatini: dilates Eustachian tube •Musculus Uvulae: shortens soft palate

Ossicles: Stapes

•Like a stirrup •Third and smallest bone of ossicular chain •Weighs 4mg •Area of 3.5mm2 •Helps to transmit sound vibrations from eardrum to oval window •Incudostapedial Joint: articulation of incus and stapes; ball-and-socket joint; head of stapes articulates with lenticular process of incus

Osseous Cochlear Labyrinth

•Looks like a coiled snail shell •Coils from its base near the vestibule •Wraps around itself 2 5/8 times before reaching its apex

Deficits of Oral-Preparatory Stage

•Loss of sensation and weak buccal muscles à pocketing food in lateral and anterior sulci •Weak mastication muscles à unchewed food •Weak lingual muscles à poor mixing of salvia with food, inadequate bolus formation, and difficulty compressing bolus onto hard palate •Compromised soft palate muscles à velum not fully depressed, permitting food to escape into nose or pharynx before initiation of pharyngeal reflexes (life-threatening) •Anterior Spillage àweak labial seal; liquids/foods can spill outside of lips, to vermillion border or down the chin

Mandibular Muscles

•Masseter: elevates mandible •Temporalis: elevates mandible •Internal Pterygoid: elevates mandible

Mandibular Muscles

•Masseter: elevates mandible •Temporalis: elevates mandible, retracts and protrudes mandible •Medial Pterygoid: elevates mandible; moves mandible and grinds mandible laterally •Lateral Pterygoid: protrudes and grinds mandible

Nutrition of the Neonate

•Mastication & Deglutition development in infants rely on maturation of their nervous system and stability of their neck, head, and trunk. •At birth, infants depend on reflexive responses. Rooting reflex: •Infant responds to tactile stimulation of perioral region (lips/cheek); infant's head rotates toward stimulus and mouth opening Sucking reflex: •Allows infant to receive food from mother's breast through a piston-like tongue protrusion and retraction resulted from soft tactile contact with the inner margin of the lips/upper lip or visual presentation of food source in older infants.

Mastication & Deglutition (cont'd)

•Mastication & Deglutition require the integration of lingual, velar, pharyngeal, and facial muscle movement with laryngeal adjustment and respiratory control. •Refer to muscles from Chapters 2, 4, and 6. Many are important in chewing and swallowing!

Summary

•Mastication and Deglutition are governed by unconscious, automatic, sensorimotor systems but can be consciously controlled. •Centrally generated processing (CPG): •Two networks in the medulla oblangata •Dorsal Swallowing Group: generates swallow pattern •Ventral Swallowing Group: activates motor response

Mastication & Deglutition

•Mastication: chewing; process of preparing food for swallowing •Moving the unchewed food onto the grinding surface of the teeth •Chewing it •Mixing it with salvia •Deglutition: process of swallowing the food •Bolus: ball of food or liquid to be swallowed

Iowa Pressure Instrument (IOPI)

•Measures tongue force •Involves pushing against a flexible ball that measures force •Force measurement may translate directly into a person's ability to: •Move a bolus in the mouth or •Squeeze the tongue onto the roof of the mouth to support movement of the bolus in swallowing

Malformations of Pinna & EAM

•Meatal Atresia: absence of EAM •Microtia: small auricle •Polyotia: parts of auricle duplicated (e.g. a second tragus) •Pre-Auricular Tags: prominences that form prenatally anterior to the pinna •Cryptotia: congenital atresia or maldevelopment of upper portion of the ear •Anotia: complete absence of the pinna •Stahl's Ear: pointy, elfin-shaped ears

Muscle Stretch & Tension Sense

•Muscle Stretch: sensed by muscle spindle fibers; found predominately in larger muscles and also found within the oral musculatures •Mandibular elevators (e.g. masseter, temporalis, lateral & medial pterygoid, genioglossus, palatoglossus) richly endowed with sensors; facial muscles lack muscle spindles •Muscle spindle fibers return a muscle to its original position following passive stretching •Muscle Tension: sensed by golgi tendon organs (GTOs) found within tendons and fascia; respond to active contraction of muscles/tension •Muscle Tone: perception of resistance to the passive movement of stretching

Tongue Muscles

•Mylohyoid: elevates floor of mouth •Geniohyoid: elevates hyoid; depresses mandible •Digastric: elevates hyoid; depresses mandible •Superior Longitudinal: elevates trip; deviate tip •Inferior Longitudinal: depresses tip; deviates tip •Vertical: cups and grooves tongue •Genioglossus: moves tongue body; cups tongue •Styloglossus: elevates posterior tongue Palatoglossus: elevates posterior tongue

Tongue Muscles

•Mylohyoid: elevates hyoid and tongue •Geniohyoid: elevates hyoid and larynx; depresses mandible •Digastricus: elevates hyoid and larynx •Genioglossus: retracts tongue •Stylohyoid: elevates hyoid and larynx •Hyoglossus: elevates hyoid •Thyrohyoid: elevates hyoid •Superior Longitudinal: elevates tongue •Inferior Longitudinal: depresses tongue •Transverse: narrows tongue •Vertical: flattens tongue

Thermal Receptors & Pain Sensors (cont'd)

•Nociceptors (pain sensors) are the same as thermal ones but have different functions: •Produce perception of pain when traumatized (e.g. burning sensation) •Important in development of structural disorders of swallowing •May respond to mechanical or thermal trauma

Deficits of Esophageal Stage

•Non-treatable by SLP (usually Gastroenterologist) •Gastroesophageal Reflex Disease (GERD): life-threatening condition in which acid from stomach enters esophagus or pharynx •Acid may flow into airway during supine position and aspiration •Lower esophagus sphincter relaxes à gastric acid enters esophagus •Weakened upper sphincter à acid enters pyriform sinus, assaulting pharyngeal tissue •Hiatal Hernia: stomach herniates through esophageal hiatus; lower esophageal sphincter may malfunction which will allow reflex into the esophagus

Sensations

•Numerous preceptors of stimuli are critical for completion of chewing, sucking, and swallowing routines (CSS) and each plays a critical role in successful completion of CSS routines. •Gustatory (taste) •Tactile (touch) •Temperature (thermal)Pressure •Pain (nocieception)

Tastes (cont'd)

•Nutritional needs govern our selection of sweet, umami, and salty tastes •These tastes elicit salivation and ingestive responses including protrusion of tongue to receive food, release of insulin, mastication, and deglutition. •In contrast, bitter and sour tastes typify poison and elicit protective responses such as gagging (elevation of larynx, clamping of VFs, elevation of velum, protrusion of tongue), coughing (tightly closing VFs, compressing abdomen and thorax, forcefully blowing VFs apart), apnea, and salivation. •Tastes can elicit motor responses that may or may not be under volitional control. •Deglutition is made up of a complex motor response dictated by the stimuli in oral and pharyngeal cavities.

Oral-Pharyngeal Structures of an Infant

•Oral cavity is smaller than adult •Larynx is more elevated •Hyoid is elevated and forward •No dentition •Larger velum

Pressures of Deglutition

•Oral, pharyngeal, and esophageal pressures move the bolus •During oral-prep stage, oral and pharyngeal cavity pressures are equalized to atmospheric pressure (because nasal airway is open) •In oral stage, velum tightly closed; tongue squeezes bolus posteriorly; positive pressure created by tongue movements that propel bolus toward the pharynx •Pharyngeal wall compresses bolus; positive pressure to prompt bolus toward the esophagus •Bolus moves toward lower pressure

Structures of the Middle Ear

•Ossicles (Ossicular Chain) -Malleus -Incus -Stapes •Muscles •Medial Wall •Anterior Wall •Posterior Wall •Floor •See Table 9-2: Landmarks of the Middle Ear

Organizing Physiological Principles of the Auditory System

•Outer Ear: collects sound; "shapes" frequency components •Middle Ear: matches airborne acoustic signals with fluid medium of cochlea •Inner Ear: performs temporal and spectral analyses on ongoing acoustic signal •Auditory Pathway: conveys and further processes the signal •Cerebral Cortex: interprets the signal

The Outer Ear (cont'd)

•Outer ear has no active/movable elements à has only a passive effect on input stimulus •Pinna & EAM have shapes that boost the relative strength of the signal through resonance à enhance signal intensity between 1500 Hz and 8000 Hz. •Pinna contributes a relatively smaller amount to overall gain as compared with that of EAM •Contribution of entire system results in net gain reaching 20 dB at approximately 2100 Hz.

Middle Ear: Medial Wall (purple)

•Oval Window: footplate of stapes is embedded; lies in the superior-posterior aspect •Round Window: below oval window; marks entrance into the scalatympani of the cochlea (tympanic duct) •Promontory of the Cochlea: bulge created by basal turn of cochlea •Prominence of Facial Nerve

Pain Reflex

•Pain withdrawal reflex affects mastication and swallowing •Causes a natural withdrawal from noxious stimulus •Oral and pharyngeal pain responses •Individual acts to remove excessive hot or spicy food by swallowing or expectoration •Tongue or mucosa lesion present, you become very aware and attempt to avoid area if possible

Soft Palate Muscles

•Palatoglossus: depresses velum •Palatopharyngeus: depresses velum

Pharyngeal Muscles

•Palatopharyngeus: constricts oropharynx to channel bolus •Salpingopharyngeus: elevates pharynx •Stylopharyngeus: raises larynx •Middle Constrictor: narrows pharynx •Inferior Constrictor: narrows pharynx

The Inner Ear

•Performs spectral (frequency) and temporal acoustic analysis of incoming acoustical signal •Components of inner ear function -Vestibular mechanism -Auditory mechanism -Electrical potentials -Neural responses -Auditory pathway responses

Neural Responses (cont'd)

•Period Histograms: -Period histograms display the point in the cycle of vibration at which firing occurs -Degree of phase-locking is presented in the major peak of figure •Phase-Locking: quality of a neuron wherein it responds to the period of the stimulus -Histogram becomes more peaked (showing greater degree of phase locking)

Reflexes in Mastication & Deglutition (cont'd)

•Pharyngeal reflex is initiated by similar contact with fauces •posterior tongue base or valleculae by bolus •Determination of whether these two reflexes result in ingestion or expulsion of bolus depends on nature of stimulus •When bolus is propelled posteriorly, orbicularis orisbuccinator, risorius, masseter, temporalis, medial pterygoid, and superior constrictor contract; which in turn pulls the superior contractor forward by virtue of its attachment •If bolus is palatable, middle and inferior constrictors will assist in ingestion, whereas an unpalatable bolus would stimulate an opposite response

Neural Responses (cont'd)

•Place Theory of Hearing: frequency resolution of cochlea occurs as a result of place of stimulation by the traveling wave, being relayed to auditory nervous system in the form of individual nerve fiber activation •Post stimulus time (PST) histogram provides support for this theory

Posterior Vertical Canal

•Posterior vertical canal is oriented roughly parallel to the long axis of the temporal bone •Its ampulla is housed in the lower crus, entering the vestibule below the oval window

The Middle Ear (cont'd)

•Pressure = Force/Area -To increase pressure: •Increase force •Decrease area over which force is being exerted •Middle ear mechanism decreases area to increase pressure to match impedance of the outer and inner ear/cochlea •Designed as an impedance-matching device -Increases pressure of signal arriving at cochlea

Pharyngeal Manometry

•Pressure measure of oral and pharyngeal structures •Esophageal Manometry: pressure measure of esophagus

The Outer Ear

•Primarily a sound collector •Shapes frequency components of sound •Pinna helps in localization of sound in space •Pinna with ridges & grooves is the best funnel for sound directed toward the head from the front or side (less effective for sound arising from behind the head) •Funnels acoustical information to the external auditory meatus àexternal auditory meatus funnels sound to the tympanic membrane

Reflexive Circuits

•Processes dealing with eating and drinking: •Chewing, rooting, sucking reflexes •Uvular, gag, retch, vomit reflexes •Cough reflex •Pain reflex •Apneic reflex •Respiration reflexes •Mediated at the level of the brainstem (do not need cortical control)

Middle Ear: Posterior Wall & Floor (orange/green)

•Prominence of the stapedial pyramid from which the tendon of stapedius arises before attaching to the neck of the stapes •Floor of Middle Ear: -Jugular bulb -Mastoid air cells comprising mostly of mastoid process of temporal bone may extend to floor of middle ear -Infection of middle ear (otitis media) may result in infection of mastoid cells (mastoidits) •If not treated, meningitis (brain case infection) may occur; life-threatening condition

Apneic Reflex

•Protective response that is active during swallowing •Eliciting through stimulation of the oral cavity, pharynx, or larynx •Results in adduction of the vocal folds, elevation of the larynx, inversion of the epiglottis, and cessation of respiration

Electrical Potentials

•Resting or Standing Potential -Voltage potential differences that can be measured from the cochlea at rest -Ions do not travel between endolymphatic portions (scala media) and those filled with perilymph (scala tympani and scalavestibuli) •There are cochlea potential differences between these two spaces -Scala media is considerably move positive (about +80mV); scalamedia has a constant positive potential (endocochlearpotential) compared to scala vestibuli and scala tympani •Scala vestibuli is slightly more positive than scala tympani (about +5mV)

Outer Ear: Pinna (cont'd)

•Scaphoid Fossa: between helix and antihelix •Crura of Antihelix: antihelix bifurcates superiorly, producing crucaantihelices •Triangular Fossa/Fossa Trangularis: space between crura of antihelix •Lobule/Lobe: below antitragus; devoid of cartilage •Intertragic Incisure: region between tragus and antitragus

Osseous Semicircular Canals (cont'd)

•Semicircular canals are open to vestibule by apertures (vertical canals, anterior and posterior share one aperture called crus commune) •Near opening to vestibule in each canal there is an enlargement housing the ampulla

Vestibular Mechanism

•Semicircular canals provide major input to proprioceptive system -Responsible for the sense of one's body in space •Each canal is at right angle to the other canals; all movements of head can be mapped •As head rotates, fluid in canals lag behind; cilia are stimulated by movement of fluid during rotation •Utricle & saccule sense acceleration of head rather than rotation during body or head tilting -Utricle: (horizontal) straight-line acceleration in a forward or backward movement -Saccule: (vertical) sensation associated with rapid acceleration during take-off of a jet; or sinking feeling during sudden drops

Olfaction

•Sense of smell. •Plays vital role in appetite and taste: •Molecules arising from food pass over olfactory chemoreceptors to increase magnitude of taste perception (why food tastes flat in nasal congestion) •Unpleasant food odors produce gagging or vomiting •Pleasant food odors produce salivation

Tactile Sense

•Sense of touch •Mediated by many mechanoreceptors = sensors that are sensitive to physical contact •Broadly distributed about the body •Differentiated by the type of stimulus causing the response Glabrous (hairless) skin contains: •Messiner's corpules and Merkel disk receptors which transmit movement and pressure Deep cutaneous skin contains: •Pacinian Corpules and Ruffini Endings which respond to deep pressure and stretch Vibration Sense: subclass of tactile sense; sensed by deformation of tactile receptors •Two-Point Discrimination: measuring sense of touch by perceiving two probes as two versus one stimulus

Deficits of Pharyngeal Stage

•Sensory and motor deficits can be very dangerous at this stage of swallowing. •Slowed velar elevation à nasal regurgitation •Reduced sensation at the fauces, posterior tongue, pharyngeal wall or soft palate may result in elevated threshold for the trigger of the swallowing reflex •Reduced function of the pharyngeal constrictors may result in slowed pharyngeal transit time of the bolus in which the individual may prematurely re-intitate respiration •Weakened pharyngeal function may result in residue left in the valleculae •Failure of the hyoid and thyroid to elevate and full epiglottic inversion may result in loss of airway protection (aspiration & penetration)

Ossicles: Incus

•Shaped like an anvil •Weighs 30mg •7mm long •Provides intermediate link of ossicular chain •Incus and malleus articulate by means of a saddle joint with limited movement; malleus and incus move as a unit upon movement of the TM

Electrical Potentials (cont'd)

•Stimulation of hair cells result in numerous potentials Cochlear Microphonic Potential -Alternating current potential (AC) -Generated by outer hair cells Summating Potential -A sustained direct current (DC) shift in endocochlear potential that occurs upon stimulation of Organ of Corti by sound -IHC are depolarized when stimulated by sound; results in reduced intercellular potential (a less negative potential) -This potential difference between hair cells and endolymph may produce summating potential which is maintained as long as auditory stimulus is presented to the ear Whole-Nerve/Compound Action Potential (AP) -Arises from simultaneous stimulation of hair cells; sum of action potentials generated by stimulation of hair cells -Elicits action potentials in VIII nerve neurons

Swallow Pattern of Neonate

•Sucking reflex involves protrusion of the tongue with sufficient force to start flow of milk from breast •Repeated forward pumping of tongue-mandible unit results in milk entering t he oral cavity •After 4 -5 thrusts of tongue, swallow is triggered with tongue base lowered to permit milk to enter oropharynx during next forward pumping action of tongue. •Velum of infant "locks" into space between epiglottis and tongue at the location of the valleculae •Action seals off infant's airway; bolus cannot enter respiratory passageway •Infant can breathe while swallowing although swallowing includes an apneic period in which respiration stop

Gustation

•Taste •Critical component of CSS •Taste receptors (buds or cells) are chemoreceptors for gustation •They respond when specific chemicals come in contact with them •Transmit information to the brain about taste •Found interspersed in the epithelia of tongue within papillae (prominences) •Opening in the lingual epithelium houses taste buds is called taste pores

Auditory Mechanism: Mechanical Events (cont'd)

•The Traveling Wave -Sound is disturbance in air -Airborne disturbance moves TM à TM movement is translated to oval window -When TM moves inward, stapes footplate in the oval window also moves in -When TM moves outward, stapes footplate in oval window also moves outward -When stapes compresses the perilymph of scala vestibuli, Ressiner's membrane is distended toward scala media; basilar membrane is distended toward scala tympani -Compression of the fluid of the scala vestibuli is translated directly to the basilar membrane

Auditory Mechanism

•The auditory mechanism is responsible for processing the acoustic signals of speech. •Acoustic signal has an amazing range of sound pressure. -Frequency range of around 10 octaves spanning 20 -20,000 hertz. •An octave is a doubling in frequency (in music, an octave is a series of eight notes occupying the interval between (and including) two notes, one having twice or half the frequency of vibration of the other).

Auditory Mechanism: Mechanical Events

•The cochlea -Most awe-inspiring sensory system of the body •As big as an eraser on your pencil; fluid inside would be a small drop on the tabletop -Establishes first level of auditory processing of incoming acoustic signals (spectral temporal analyses) •Determines frequency components of signals •Determines amplitude of signals •Identifies temporal aspects of signals -Further analysis will occur in the brain

Middle Ear Function

•Three impedance matching systems •Area Parameter of TM and Oval Window -Sound energy reaching the TM is funneled to the smaller area of the oval window for gain -Area ratio provides a 25 dB gain (TM (55mm2) to oval window (3.2mm2), approx. 17:1 (~25 dB) •Lever Difference -Length of manubrium (9mm), long-process of stapes (7mm) -Level advantage of ossicles provides a 2 dB gain (overall gain 1.2)

Salivation (cont'd)

•Three major glands •Parotid Gland: secretes serous saliva into pharynx •Submandibular Gland: produces thin and thick secretions serving as lubricant to bolus and opens into the oral cavity lateral to lingual frenulum •Sublingual Gland: produces thick mucus, empties into mouth, helps in formation of bolus Mucus: secreting accessory salivary glands throughout oral cavity; embedded within the mucosa (activated by stimulation of taste receptors in anterior 2/3 of tongue)

Osseous Cochlear Labyrinth (cont'd)

•Three openings: -Round Window (foramen rotunde): communicates between scalatympani and middle ear -Oval Window: stapes is place; communicates between scalavestibuli and middle ear space -Cochlea Aqueduct (canaliculus): connects upper duct and subarachnoid space of cranial cavity; hypothesized that perilymph passes through here

Oral Preparatory Stage (Mastication)

•Tongue moves food onto grinding surface of teeth to be mixed with saliva •Food ground up by lingual muscles and muscles of mastication •Food mixed with saliva to form bolus •Buccal wall muscles (risorius & buccinator) contract to keep food from entering lateral sulcus (between gums & cheeks)

Chewing Reflex

•Triggered by deep pressure on the roof of mouth (as when you bite a cracker) •Involves rotary motion of mandible by alternating left-side and right-side contraction of mandibular elevators (masseter & medial pterygoid) •With the depression of mandible afterward, lingual muscles can move bolus into and off of the molars •Chewing center is located within the midbrain •Center involved in reflexive movements of tongue for sucking and licking as well

Neural Responses (cont'd)

•Tuning Curve: a measure of neural specificity or basilar membrane response -A composite of a single fiber at each frequency of discrimination -The sharper the tuning curve, the greater the frequency of the basilar membrane -Researchers placed an electrode on a neuron and then presented different frequencies; recorded stimulus intensity at which neuron started to fire in response to stimulus and then plotted that intensity

Organ of Corti (cont'd)

•Tunnel of Corti separates inner and outer cells •Stereocilia protrude from surface of hair cells; stereocilia in apex are longer than the ones in the base; movement of one cilia disturb adjacent cilia •Tectorial Membrane: overlays hair cells •Inner hair cells innervated by many nerve fibers; do not have physical contact with tectorial membrane •Outer hair cells innervated by one nerve fiber; embedded in tectorial membrane

Neural Responses

•Two basic types of CN VIII neurons -Low-Spontaneous Rate (High-Threshold) •Require higher level of stimulation to fire •Encompass higher end of auditory range of signal intensity •Elicits little or no background firing noise •Processes higher level sounds -High-Spontaneous Rate (Low-Threshold) •Respond at very low signal intensities •Display random firing even when no signal is present •Process near-threshold sounds

Outer Ear: Tympanic Membrane (cont'd)

•Umbo: most distal point of attachment of the inner TM to the malleus •Cone of Light: inferior and posterior to umbo; reflects light of otoscope •Manubrium: handle of malleus behind TM (looks like a handle of a clock pointing to 1 at the left ear) •Pars Flaccida: superior quadrant of TM; doesn't have fibrous tissue

Respiratory Reflexes

•Under partial voluntary control •Respiratory centers located in lower medulla •Individual inspiratory and expiratory centers (separated) •Excitation of inspiration inhibits expiratory muscles and vice versa Respiratory centers located in lower medulla sensitive to level of oxygen and carbon dioxide in blood or blood acidity changing the respiratory rate: •Inadequate oxygenation in the blood •Increased carbon dioxide in the blood •Increased acidity

Pharyngeal Stage (cont'd)

•Upper Esophageal Sphincter Action: UES consists of cricopharyngeus muscle which relaxes and opens up as the larynx and hyoid move up and forward •When a person is not swallowing (e.g. during respiration), the UES is tonically contracted which keeps gastric contents from escaping into the laryngopharynx (esophageal reflux)

Deficits of Oral Stage

•Usually either sensory and/or motor dysfunctions. •Weakened Movements à reduced oral transit time (time required to move bolus to the point of initiation of the pharyngeal state) of bolus toward pharynx and/or remaining food on the tongue or hard palate after transit •Oral-Phase Involvement à Tendency for epiglottis to fail to close laryngeal opening and to have limited hyoid elevation; pooling food or liquid within vallecula •Sensory Deficit à difficulty initiating reflexive swallow;thermotactile feedback or stimulus to faucial pillars may help initiate swallow

Vestibular System (cont'd)

•Utricle macula is the sensory organ which is endowed with hair cells and cilia •Saccule lies near scala vestibuli in the vestibule •Utricle & saccule communicated by the endolymphatic duct (embedded in dura mater) •The saccule communicates with cochlea by means of the minute ductus reuniens

Uvular & Gag Reflexes

•Uvular (Palatal) Reflex: mediated in manner similar to gag reflex •Gag (Pharyngeal) Reflex: elicited by tactile stimulation (light or deep touch) of faucial pillars, posterior pharyngeal wall, or posterior tongue near lingual tonsils •Both help individuals avoid averse stimuli •May be elicited by taste •Causes respiration to cease •Causes pharynx to elevate and constrict

Structures of the Inner Ear (cont'd)

•Vestibule •Semicircular Canals •Cochlea •Bony Labyrinth cavities within these structures -Perilymph •Membranous Labyrinth deep to bony labyrinth -Endolymph

Pharyngeal Stage (cont'd)

•Vocal folds tightly adduct; false vocal folds constrict •Epiglottis descends to cover laryngeal inlet assisted by aryepiglottic muscles •Larynx and hyoid bone move up and forward •When food reaches the laryngopharynx, it passes over epiglottis through the pyriform sinuses to the esophagus •At the level of the epiglottis, bolus is divided into equal masses; passing the pyriform sinuses on either side of the larynx and is recombined at esophageal entrance •Food propelled down the pharynx toward the esophagus by sequential contraction of superior, middle, and inferior pharyngeal constrictors.

The Traveling Wave (cont'd)

•Wave-like action of basilar membrane -Determines frequency data going to brain -Arises from stimulation of perilymph of vestibule -Moves along basilar membrane until it reaches point of maximum growth -Wave damps after reaching maximum growth -Only one true strong point of disturbance from the traveling wave -The place of maximum disturbance determines the frequency information that is transmitted to the brain -The point of maximum amplitude excursion of the traveling wave on the basilar membrane is primary point of neural excitation of hair cells within the Organ of Corti

Frequency Selectivity

•We can perceive 1% change in frequency •Precision of basilar membrane in frequency selectivity is reflected in the sharpness of the tuning curve •Perception is logarithmic based: -We can hear a 1 Hz difference at 100Hz or a 10Hz difference at 1000Hz -Low-frequency fibers sharper than high-frequency fibers, based on a Q10 value

Neural Responses (cont'd)

•When a VIII nerve fiber responds to tonal stimulation, there is an initial burst of strong activity, followed by a decline to a plateau of discharge over the duration of the tone. •When the tone is terminated, the response of the fiber drops to below baseline levels, rising up to the baseline noise level after recovery.

Esophageal Stage (cont'd)

•When bolus enters upper esophageal sphincter for transit to stomach, the cricopharygeus contracts again, larynx and velum will be depressed again and respiration begins again. •In a natural swallow, respiration is suspended for only about one second. •Re-initiation of respiration increases pressure in laryngopharynx. •Food at the level of the laryngeal entryway will typically be blown clear and propelled to the pharynx as most people exhale after swallowing.

Outer Ear: EAM (cont'd)

•You cannot see the medial end of the canal without manipulating the pinna and use a speculum •Outer third of EAM is lined with hairs •Cerumen (ear wax) present to trap insects and dirt protecting medial-most point of the outer ear and tympanic membrane

Tongue Muscles

Mylohyoid: elevates tongue and floor of mouth Superior Longitudinal: elevates tongue tip Vertical: cups and grooves tongue Genioglossus: moves tongue body; cups tongue Styloglossus: elevates posterior tongue Palatoglossus: elevates posterior tongue